var nav = document.querySelectorAll(".xz > li");
var main = document.querySelectorAll(".main > div");
for (var i = 0;i<nav.length;i++){
    nav[i].index=i;
    nav[i].addEventListener('mousemove',function () {
        for (var k = 0;k<nav.length;k++){
            nav[k].classList.remove('active');
            main[k].classList.remove('active');
        }
        this.classList.add('active');
        main[this.index].classList.add('active');
    })
}